Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

I have a Lennox G20Q2E that appeared dead. The 2 amp glass fuse was blown. I replaced it and the fuse remained good with no call for heat. Stat called for heat and the electric damper started to open then the fuse blew and the wall stat started to smell of smoke. I dont see many Lennox products and have seen none with a motorized damper. Is the relay board causing the fuse to blow or is one of the devices hooked to it loading it down? Why did the stat heat up so fast? Why does this natural draft unit have a motorized damper? thanks for any help!!!

Now the freaks are on television, the freaks are in the movies. And its no longer the sideshow, its the whole show. The colorful circus and the clowns and the elephants, for all intents and purposes, are gone, and were dealing only with the freaks. - Jonathan Winters

thanks for you input. I have isolated the board but the fuse still blows with a flash of a dead short even tho I checked every wire in the furnace and disconnected all the stat wires. The fuse protects the 24 volt supply but only blows when the R and W is jumpered. The relays switch the 120 volt devices so they should not be causing any trouble. Can the board fail internally in a way that it only pops the fuse when R W make? Does the relay board have a history of this on the lennox?

It most likely is a short on the 24V side. Some of those are difficult to find and can take quite a bit of time. You might also check to see if the damper is getting stuck and the motor is pulling high amperage. That probably isn't the case but I would still check it.

the damper motor is 120 volt switched from a relay so it shouldnt load the 24 volt supply. The fuse pops so fast that its got to be a virtually dead short. But there are no dead or low ohms readings anywhere. thanks for the feedback. May have to get the board.